Fish migrate one or more times in their life, for example from a sea or ocean to fresh water and back or the other way around. Different species of fish may prefer different times in the year to migrate. The different bodies of water through which they migrate usually have different water levels, creating a need for the fish to swim up or down. Manmade barriers such as dams and locks create barriers which fish may not be able to overcome.
Providing a meandering path around or in parallel to such barriers for fish to swim through requires a large surface. EP2767635 discloses an active lift device for transporting fish from a lower situated body of water to a higher situated body of water.